Method for producing DNDA

ABSTRACT

The invention relates to a method for producing DNDA that is advantageous in economical, chemical and process engineering terms.

This application is a 371 of PCT/EP01/10023 filed Aug. 30, 2001.

Heretofore the energetic plasticizer DNDA-6-7, a ternary mixture ofN,N′-dimethylbis-nitramine (DNDA-5; approx. 43%),N-methyl-N′-ethyl-bisnitramine (DNDA-6; approx. 45%) andN,N′-diethylbisnitramine (DNDA-7; approx. 12%), has been made in thefollowing manner:

1. Nitration of N,N′-dimethylurea

1.1. Batch reaction with an acid mixture (mixture of nitric acid andsulfuric acid) with the addition of urea dissolved in dichloromethane atabout −10° C.

1.2. Stopping the reaction by pouring it onto ice water.

1.3. Collecting the reaction mixture (main product: dinitridimethylurea)in dichloromethane by shaking it out.

1.4. Neutralizing the dichloromethane with sodium hydrogen carbonate.

2. Hydrolysis of the dinitrodimethylurea.

2.1. Mixing the dichloromethane phase with water, evaporating thedichloromethane, followed by hydrolysis at about 100° C.

2.2. Collecting the methylnitramine in dichloromethane

3. Nitration of N,N′-diethylurea.

3.1. Batch reaction with a mixture of acids (mixture of nitric acid andsulfuric acid) with the addition of the urea dissolved indichloromethane at about −15° C.

3.2. Stopping the reaction by pouring it onto ice water.

3.3. Collecting the reaction mixture (main product dinitrodiethylurea)in dichlormethane by shaking.

3.4. Neutralizing the dichloromethane phase with sodium hydrogencarbonate.

4. Hydrolysis of the dinitrodiethylurea.

4.1. Mixing the dichloromethane phase with water, evaporating thedichloromethane, followed by hydrolysis at about 100° C.

4.2. Collecting the ethylnitramine in dichloromethane.

5. Condensation

5.1. Condensing the methyl and ethyl nitramine in common in a fixedratio of about 2:1 at max. 0° C. with 70% sulfuric acid andp-formaldehyde in dichloromethane.

5.2. Stopping the reaction by pouring onto ice water.

5.3. Collecting the reaction mixture (ternary mixture of the nitramines)in dichloromethane by shaking.

5.4. Neutralizing the dichoromethane phase with sodium hydrogencarbonate.

The method outlined above is not capable of producing large amounts ofthe plasticizer in an economically practical manner.

It was therefore the problem of the invention to provide a method forproducing a DNDA type plasticizer, especially a method for theproduction of DNDA-6-7.

This problem was solved by a method in which the following changes weremade in the method known in the state of the art:

Instead of the acid mixture, highly concentrated nitric acid is used ina definite excess, preferably about an 11-fold molar excess. This changemakes it possible to recycle the nitric acid; also, surprisingly fewbyproducts are formed.

The ureas are not dissolved in dichloromethane, but are used in solidform. The advantages of this variant: less volume of liquid, no dilutioneffect.

N,N′ dimethylurea and N,N′-diethylurea are not nitrated separately buttogether at max. 5° C. in the desired molar ratio, preferably a molarratio of about 2:1 (DNDA-5-7). The advantage is that process steps canbe eliminated.

The reaction mixture (main products: dinitrodimethylurea anddinitrodiethylurea) is collected in dichloromethane by counter-currentextraction. This saves process steps and the separation efficiency isoptimized.

Combined hydrolyzation of the mixture thus obtained, at about 100° C.,in the given molar ratio. Advantage: saving of process steps.

The entire reaction is performed continuously. Thus it is possible toremove the reaction heat more easily, the reaction volumes are reduced,thereby reducing potential dangers.

With the changes according to the invention, of the method known in thestate of the art, it is possible to produce DNDA directly in a highyield, with a high purity, and in the desired composition.

By means of an HPLC study it was surprisingly found that both thedesired products and the desired compositions are produced and thatadditional byproducts are not formed by this kind of conduct of theprocess of the invention.

It is expressly pointed out that it is not necessary to perform all ofthe steps of the process in the manner according to the invention. Animprovement of the method described in the state of the art is achievedwhen at least one of them is performed. An especially preferred practiceof the method, however, is the combining of all of the variants of theinvention.

The following examples are intended to further explain the inventionwithout limiting it.

Common Nitration of the Ureas:

355 ml of HNO₃ (100%) is chilled to −15° C. A mixture of 25 g ofdiethylurea and 50 g of dimethylurea was added in portions with vigorousstirring. In the meantime the temperature is not to exceed −10° C. Thestirring time after the addition is completed was another 30 min. Thereaction solution was then fed onto ice water and collected byrepeatedly, preferably four times, shaking it out in 250 ml of methylenechloride each time. Neutralization was performed with an aqueousbicarbonate solution.

Combined Hydrolysis of the Dinitrodimethyl and Dinitrodiethyl Ureas:

A mixture of 1000 ml of the above solution and 540 ml of water washeated in the oil bath. At first an evaporation of the methylenechloride phase took place at bottom temperatures of about 50° C. Afterchanging over to reflux cooling the mixture was hydrolyzed over a periodof several hours, preferably over a period of about 3 h, at a bottomtemperature of about 96° C. The separation of the nitramine mixture wasperformed by repeated shaking, preferably three times, with about 500 mlof dichloromethane each time. By evaporation in the rotary evaporatorthe nitramine solution was concentrated to about 95 ml.

Condensation:

At 0° C., 5 g of paraformaldehyde dissolved in 40 ml of methylenechloride was added to 120 ml of sulfuric acid (75%) in a receiver. The95 ml of nitramine solution from the previous step was slowly added froma dropping funnel over a period of 30 minutes, with stirring. To keepthe concentration of the sulfuric acid approximately constant, and tooptimize the yield, 96% sulfuric acid was additionally added. Thetemperature in this case should preferably not rise above 0° C. Thecondensation was stopped after about 3 h of stirring by pouring out ontoice water, and the product was again collected in methylene chloride,neutralized, washed, and concentrated by evaporation. Yield: 35 g ofDNDA-5-7.

By the method of the invention it is thus possible for the first time toproduce DNDA economically, chemically and by a practical technicalprocess, in a high yield, high purity and in the desired composition.

What is claimed is:
 1. A method comprising nitrating bothN,N′-dimethylurea and N,N′diethylurea with highly concentrated nitricacid to produce dinitrodimethylurea and dinitrodiethylurea, hydrolyzingthe dinitrodimethylurea and dinitrodiethylurea to producemethylnitramine and ethylnitramine and other reaction products; andcondensing the methylnitramine and ethylnitramine to form DNDA.
 2. Themethod according to claim 1, wherein said N,N′-dimethylurea andN,N′diethylurea are in solid form.
 3. The method according to claim 1,wherein said N,N′-dimethyurea and N,N′-diethylurea are nitratedtogether.
 4. The method according to claim 2, wherein saidN,N′-dimethyurea and N,N′-diethylurea are nitrated together.
 5. Themethod according to claim 1, wherein the dinitrodimethylurea,dinitrodiethylurea and other reaction products are collected indichloromethane by countercurrent extraction.
 6. The method according toclaim 2, wherein the dinitrodimethylurea, dinitrodiethylurea and otherreaction products are collected in dichloromethane by countercurrentextraction.
 7. The method according to claim 3, wherein thedinitrodimethylurea, dinitrodiethylurea and other reaction products arecollected in dichloromethane by countercurrent extraction.
 8. The methodaccording to claim 4, wherein the dinitrodimethylurea,dinitrodiethylurea and other reaction products are collected indichloromethane by countercurrent extraction.
 9. The method according toclaim 1, wherein said dinitrodimethylurea and dinitrodiethylurea arehydrolyzed together.
 10. The method according to claim 2, wherein saiddinitrodimethylurea and dinitrodiethylurea are hydrolyzed together. 11.The method according to claim 3, wherein said dinitrodimethylurea anddinitrodiethylurea are hydrolyzed together.
 12. The method according toclaim 4, wherein said dinitrodimethylurea and dinitrodiethylurea arehydrolyzed together.
 13. The method according to claim 5, wherein saiddinitrodimethylurea and dinitrodiethylurea are hydrolyzed together. 14.The method according to claim 6, wherein said dinitrodimethylurea anddinitrodiethylurea are hydrolyzed together.
 15. The method according toclaim 7, wherein said dinitrodimethylurea and dinitrodiethylurea arehydrolyzed together.
 16. The method according to claim 8, wherein saiddinitrodimethylurea and dinitrodiethylurea are hydrolyzed together. 17.The method according to claim 9, wherein dinitrodimethylurea anddinitrodiethylurea are hydrolyzed in common at about 100° C. in thedesired molar ratio.
 18. The method according to claim 10, whereindinitrodimethylurea and dinitrodiethylurea are hydrolyzed in common atabout 100° C. in the desired molar ratio.
 19. The method according toclaim 11, wherein dinitrodimethylurea and dinitrodiethylurea arehydrolyzed in common at about 100° C. in the desired molar ratio. 20.The method according to claim 12, wherein dinitrodimethylurea anddinitrodiethylurea are hydrolyzed in common at about 100° C. in thedesired molar ratio.
 21. The method according to claim 13, whereindinitrodimethylurea and dinitrodiethylurea are hydrolyzed in common atabout 100° C. in the desired molar ratio.
 22. The method according toclaim 14, wherein dinitrodimethylurea and dinitrodiethylurea arehydrolyzed in common at about 100° C. in the desired molar ratio. 23.The method according to claim 15, wherein dinitrodimethylurea anddinitrodiethylurea are hydrolyzed in common at about 100° C. in thedesired molar ratio.
 24. The method according to claim 16, whereindinitrodimethylurea and dinitrodiethylurea are hydrolyzed in common atabout 100° C. in the desired molar ratio.
 25. A method for producingDNDA-5-7 comprising nitrating N,N′-dimethylurea and N,N′-diethylureatogether to form dinitromethylurea and dinitroethylurea with highlyconcentrated nitric acid wherein said N,N′-dimethylurea andN,N′-diethylurea are in solid form and are in a molar ratio of about2:1; hydrolyzing said dinitrodimethylurea and dinitrodiethylureatogether; and condensing the methylnitramine and ethylnitramine to formDNDA.
 26. The method of claim 1 wherein said process is continuous. 27.The method of claim 25 wherein said process is continuous.
 28. A methodof preparing a propellant charge powder comprising producing DNDA-5-7 bynitrating in common N,N′-dimethylurea and N,N′-diethylurea to formdinitromethylurea and dinitroethylurea with highly concentrated nitricacid wherein said N,N′-dimethylurea and N,N′-diethylurea are in solidform and are in a molar ratio of about 2:1; hydrolyzing saiddinitrodimethylurea and dinitrodiethylurea together; and condensing themethylnitramine and ethylnitramine to form DNDA; and admixing the DNDAto form a propellant charge powder.
 29. A method for preparingpropellant charge powder comprising: producing DNDA by nitratingN,N′-dimethylurea and N,N′diethylurea with highly concentrated nitricacid, hydrolyzing the dinitrodimethylurea and dinitrodiethylurea toproduce methylnitramine and ethylnitramine and other reaction products;and condensing the methylnitramine and ethylnitramine to form DNDA; andadmixing the DNDA to form a propellant charge powder.
 30. The method ofclaim 1 wherein said highly concentrated nitric acid is 100% nitricacid.
 31. The method of claim 25, wherein said highly concentratednitric acid is 100% nitric acid.
 32. The method of claim 28, whereinsaid highly concentrated nitric acid is 100% nitric acid.
 33. The methodof claim 29, wherein said highly concentrated nitric acid is 100% nitricacid.
 34. A method consisting of: nitrating both, N,N′-dimethylurea andN,N′diethylurea with highly concentrated nitric acid to producedinitrodimethylurea hydrolyzing the dinitrodimethylurea anddinitrodiethylurea to produce methylnitramine and ethylnitramine andother reaction products; and condensing the methylnitramine andethylnitramine to form DNDA.